fossilized concrete jungles…underground

While these huge piles of rubble build up as humans tear old structures down and rebuild on top (which is why archeological sites of old cities rise above their surroundings), the rubble on top is chaotic. The real patterns are below:

The deep skyscraper roots form inverted concrete and steel spires beneath a New Orleans that is slowly sinking into the Gulf of Mexico, as the detritus of half a continent, washed on to the top of the Mississippi delta, presses down on the malleable crust. Around the tops of the concrete piles snake the thick tangle of pipes for water, electricity, gas, sewage, optical cables, of subways, underground carparks, and nuclear fall-out shelters. Once in the burial realm, these abandoned foundations of our human empire can begin their transformation into the Urban Stratum that may, in the yet more distant future, be discovered, analysed, explored, marvelled at.

Not all cities will fossilized, just as not all dead animals will. The conditions must be right.

What city? It might be New Orleans, or Haiphong, or Shanghai, or Amsterdam, or Venice, or Port Harcourt, or Dhaka. These are just a few of the cities and megacities that today spread across coastal plains, and over river floodplains and estuary margins. These, hence, are firmly sited on downgoing tectonic escalators, the weight of the deltaic sediment that they are built on inexorably dragging them down. And all are at or just above sea level (or just below it, in some cases, behind protective walls), so making them vulnerable to drowning by even the slightest of sea level rises. Once drowned, they will be removed from the realm of erosion into the realm of
sedimentation, as if placed in a pickling jar.

--Kevin Kelly, quoting a new book by Jan Zalasiewicz, a geologist from the University of Leicester, "The Earth After Us: What Legacy Will Humans Leave in the Rocks?"
in an intriguing essay called Fossil Cities.